The oxygen supply to the retina is crucial in maintaining visual function, but retinal oxygenation is often disturbed by vascular occlusion or disease. Management of these conditions could conceivably profit from knowledge of the normal oxygen supply, the changes that occur with vascular occlusion, and the potential for restoring oxygenation. The proposed work is designed, therefore, to further the basic knowledge of oxygen supply and consumption within the mammalian retina. Retinal oxygen supply is complex in higher mammals, since two circulatory beds nourish the retina. Measurements of vitreal oxygen tension have been made previously, but these do not allow an accurate prediction of the oxygen tension in the outer part of the retina, around the photoreceptors. The next step in understanding retinal oxygen supply is therefore to make intraretinal measurements in a mammal, the cat, that has a dual retinal circulation. The specific aims are to 1) define the normal profile of oxygen tension as a function of depth in the retina, 2) determine how this profile changes as a function of light adaptation and retinal eccentricity, 3) use this experimental data to derive information concerning oxygen consumption as a function of depth, 4) determine how the profiles and retinal function change during graded hypoxia, and 5) develop a mathematical model of retinal oxygenation applicable to disturbances of retinal oxygen supply. To accomplish these goals, intraretinal oxygen tension will be measure with oxygen microelectrodes, and retinal function will be assessed with the electroretinogram recorded intraretinally. Data obatined from the experimental measurements will be used in conjunction with diffusion theory to develop a mathematical model of oxygen supply. In the long term this work could be extended to the primate retina, and could contribute to an understanding of the neovascularization that occurs in diabetes and retrolental fibroplasia.